Why do I get the timeout warning?

I turned on debug mode in WordPress and the first request of the day I get this error:

Warning: http_request() [function.http-request]: Timeout was reached; Operation timed out after 1000 milliseconds with 0 bytes received (/wp-cron.php?doing_wp_cron) in /public/wp-includes/class-http.php on line 1218

I know what cron jobs are and I understand how WordPress might want to run periodic jobs (and since HTTP is stateless, running a “cron” job on the first request of the day makes sense) but why does it time out?